Cooling means for refrigerant compressor motors



Dec. 3, 1963 P. A. WELLER 3,112,618

COOLING MEANS FOR REFRIGERANT COMPRESSOR MOTORS Filed June 15, 1960 3 Sheets-Sheet l FIG.I

INVENTOR. PETER A.WELLER i BY 38 :21"; F IG 2 w|Lsou,Lewns =7 NkQAE ATTORNEYS Dec. 3, 1963 P. A. WELLER 3,112,618

COOLING MEANS FOR REFRIGERANT COMPRESSOR MOTORS Filed June 15, 1960 3 Sheets-Sheet 2 48 I6 2 IO I I: TILL:

t F 1 I4 42 IN V EN TOR. PETER AMlELLER Dec. 3, 1963 P. A. WELLER 3,112,618

COOLING MEANS FOR REFRIGERANT COMPRESSOR MOTORS Filed June 15, 1960 3 $heets-Sheet 3 28 IO I2 42 2 I2 42 8 IO 44 E 24 38 INVENTOR.

PETER A.WELLER FIG.6 BY

w en, LEWI5 MQPAE ATTORNEYS United States Patent 3,112,618 CQOLING MEAN FOR REFREGERANT COMPRESSSR MOTGRS Peter Anthony Weller, Farmingtcn, Mich, assign'or to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed June 15, 1959, Ser. No. 36,256 13 Claims. (Cl. 6211'7) This invention relates to refrigerating systems, and

particularly to means for cooling the compressor motors in such systems.

In systems wherein the refrigerant compressor is operated by an electric motor the service life and capacity of the system is materially reduced unless provision is made for adequately cooling the compressor motor. It has previously been proposed to cool refrigerant compressor motors by means of an auxiliary cooling water circuit including a jacket structure surrounding the-motor for removing the unwanted heat from the motor parts. Such systems have not always given the desired cooling, and have additionally sufllered by reason of relatively high construction costs, high installation costs, and high maintenance costs.

It is an object of the present invention to overcome the above-mentioned disadvantages of the previous proposals and to provide a novel compressor motor cooling system in which liquid system refrigerant is injected into the motor under such pressure and at such velocity as to be substantially completely vaporized during its travel adjacent the motor parts.

It is a further object of the invention to provide a compressor motor cooling system of the above-mentioned character, wherein the liquid refrigerant is injected into the motor coo-ling mechanism under a higher pressure than the system pressure, whereby to permit the sprayed refrigerant to reach various potential hot spots located remote from the point of injection.

A still further object of the invention is to provide a compressor motor cooling arrangement of the above type wherein an auxiliary pump is utilized to raise the pressure of refrigerant supplied to the motor-cooling mechanism, thereby permitting the compressor motor to be adequately cooled even when the refrigerant system has arelatively low operating pressure.

A still further object of the invention is to provide a refrigerant compressor motor cooling system of the abovementioned type, wherein only a part of the refrigerant in the system is by-passed into the motor-cooling mechanism so as to thereby enable the motor to be cooled to a desired extent without cooling the motor more than is necessary for proper operation. i

Another object is to provide method and apparatus for cooling an electric machine having a rotor and stator.

A further object of the invention is to provide a compressor motor cooling system having a minimum number of fluid lines, control'valves, and points of possible leakage so as to promote trouble-free operation and reduced maintenance costs.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a schematic view illustrating one embodiment of the invention;

FIG. 2 is a view similar to FIG. 1 but illustrating a second embodiment of the invention;

FIG. 3 is a view similar to FIG. 1 butillustrating a third embodiment of the invention;

FIG. 4 is a schematic view illustrating a still further embodiment of the invention;

FIG. 5 is a schematic. view illustrating another form of the invention; and

FIG. 6 is an additional view illustrating a further embodiment of the invention.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to'the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, and particularly FIG. 1, there is shown a refrigerating system comprising a centrifugal compressor 10 operated by the electric motor indicated generally by numeral 12. The compressor is provided with an impeller having the usual radial vanes for pumping the evaporated refrigerant from the suction line 14; into the outlet scroll 16. The scroll feeds hot gas into the line 18 which discharges into the tube-shell type condenser 2t Condensed refrigerant is discharged from the condenser to a liquid line 22 which empties into the trap chamber 24. The trap chamber is provided with a butterfly valve 26 suitably operated from the float 28, as by means of the thrust rod 30 and link 32. The trap chamher is provided with an outlet opening at 34, the arrangement being such as to prevent condenser gas from entering line 36. In operation, any tendency toward lowering of the liquid level in chamber 24 causes the float 28 to be depressed so as to open the valve 26 and thereby maintain the liquid level well above the outlet opening 34 within the upstanding portion of the trap chamber. Conversely, any tendency of the liquid level in chamber 24 to be raised above the design value will cause the float 28 to close the valve 26 and thereby maintain the liquid level in the trap chamber. In this manner no gas from the condenser can enter line 36. The drawings are semi-schematic in character and the trap chamber is shown somewhat enlarged relative to certain of the other components, in order to better illustrate its operational details. In actual practice the trap chamber is relatively small as compared with the evaporator and condenser.

' Line 36 feeds liquid refrigerant to the tube-shell type evaporator 38, from whence it is discharged as a vapor into the suction line 14 for the compressor 10, thus completing the circuit. The impeller for compressor 10 is rotated at high speed by the electric motor 12 which is provided with the conventional rotor structure 40, stator structure 42, and gap 43 therebetween. In the illustrated embodiment the motor is preferably formed as a sealed device and is provided with an end cap or hell 44 having an orifice 46 therein for receiving liquid refrigerant from the small diameter line 48. Line 48 receives liquid refrigerant from the aforementioned line 22, and because of the size of-the orifice 46 only a relatively small part of the liquid refrigerant discharged from condenser 2t! is directed into the motor housing. By this arrangement the refrigerating system of condenser and evaporator is enabled to operate efliciently without excessive subtraction of refrigerant and without overcooling of the motor 12. The relative amount of liquid diverted from line 22 into line 48 may be varied in accordance with such factors as capacity of the system, motor size, and design temperatures of the motor and system. In the usual situation however the diverted refrigerant is only a small percent of the total refrigerant, as for example two or three percent. In mos-t cases the diverted refrigerant would be less than ten percent.

In order to most effectively and uniformly cool the motor the spray orifice 46 preferably distributes all or a substantial part of the refrigerant directly into gap 43 (where the temperatures are usually highest). If necessary the orifice structure can be formed as a series of nozzles located within bell 44 in line with gap 43.

In the illustrated embodiment the refrigerant travels through the motor windings and is then discharged into a line 50 in the gaseous state. Preferably line is of greater diameter than orifice 46 so that the pressure in line '50 does not rise excessively such as might interfere with proper circulation of refrigerant through the motor. As previously noted, the amount of refrigerant devoted to cooling of motor 12 is relatively small as compared with the amount of refrigerant in line 36. Therefore the introduction of vaporized refrigerant from line 59 into line 36 does not appreciably interfere with proper operation of the evaporator. For high cooling action the quantity of liquid refrigerant introduced into the motor is somewhat in excess of that which can be vaporized so that there will be some liquid refrigerant returning with the gas in line 56.

FIG. 1 of the drawings illustrates orifice 46 as a fixed size orifice. FIG. 2 illustrates a refrigerating system which is identical with the PKG. 1 system, except that a small liquid pump 52 which is preferably operated from a small auxiliary motor (not shown) is inserted in line 48. This pump takes liquid from the line 48 and appreciably increases its pressure as it is discharged into the line 48a. By this arrangement the refrigerant can be fed through the compressor motor at a relatively high pressure such that it is allowed to reach all hot spots in the motor prior to vaporization.

The pump 52 is of particular advantage in those types of systems wherein the liquid pressure in line 36 is relatively low, since by using the pump satisfactory quantities of refrigerant can be fed through motor 12, even though the pressure in line 48 would otherwise be insufiioient for proper flow of refrigerant.

By suitable control structure the output pressure of the pump 52 can be varied and controlled so as to provide a further regulation of the character of the motor cooling operation in accordance with different systems and variations in operation of any particular system in which the pump is utilized.

The construction and arrangement shown in FIG. 3 is in many respects similar to the arrangement of FIG. 1, and corresponding numerals are therefore employed wherever applicable. In the FIG. 3 arrangement the condenser 20 is provided with two outlets 56 and 5%. Outlet 56 feeds liquid refrigerant into the line 66' which discharges into the upper portion of the trap chamber 24. The trap chamber is provided with the butterfly valve 26 and operating float 28, the arrangement being such that as the liquid level in the trap chamber tends to be lowered the valve 26 tends to be closed so as to discontinue the [feeding of liquid into the line 36 and prevent any gas in line 60 from entering line 36. When sufficient liquid refrigerant is discharged from line 69 into the trap chamber 24 the float 28 is raised so as to open valve 26 to the line 36.

The discharge 58 from condenser 29 is preferably formed as a small sump structure having a side wall 62 and bottom wall 64. Line 48 extends from bottom wall 64 to feed liquid refrigerant to the orifice 46, and the intended mode of operation of the FIG. 3 embodiment is the same as that of the FIG. 1 embodiment.

The advantage in utilizing a small sump as in FIG. 3 resides in the fact that line 4-8 is thereby always assured of a supply of gas-free liquid refrigerant irrespective of variations in dischargeconditions which might occur at various times in the operation or the condenser 20.

The embodiment of FIG. 4 is similar to the FIG. 3 embodiment except that a liquid pump 52 is provided in line 48. Pump 52 serves the same purpose as the corresponding pump in the FIG. 2 embodiment, namely as a device for raising the pressure of the liquid prior to its discharge into the motor so as to provide adequate cooling in those installations having relatively low operating pressures.

Referring to FIG. 5, there is disclosed an arrangement wherein condensed liquid is discharged from the condenser 29 through the line 60 and thence into the upper portion of the trap chamber 24. The liquid collects therein and is fed into the liquid line 36 under the control of the float 23 as in the previously described FIG. 3 arrangement. Line 36 feeds liquid refrigerant into the lower portion of evaporator 38, said evaporator having a discharge port 66 in its bottom wall for delivering liquid refrigerant to the line 68. Line 63 delivers the liquid refrigerant to a pump 52 which raises the liquid pressure before discharging the refrigerant into the compressor motor 12.

The embodiment of FIG. 5 differs from the previously described embodiments in that all of the refrigerant from the condenser 2 .5 is fed into the line 36, i.e., there is no bypassing of a portion of the refrigerant, as by means of the previously discussed line 48. The system of FIG. 5 incorporates a bypass function as part of the evaporator 38 since the flooded portion of the evaporator serves as a liquid sump for supplying liquid to line 68. The amount of line 6% liquid in relation to the amount of line 36 liquid is preferably relatively small, as by suitable sizing of the lines. By such an arrangement it is possible to provide desired cooling of the motor 12 without such excessive motor cooling as would seriously reduce the capacity of the system by subtraction of refrigerant. In a particular design the amount of motor cooling would preferably be such as to maintain a compressor motor temperature of perhaps E, which temperature can generally be withstood by most present day motors.

Referring to FIG. 6, there is shown a refrigerating system wherein the condenser 20 discharges liquid refrigerant into a line 60 leading to the upper portion of the trap or float chamber 24. The lower portion of the chamber 24 is provided with a valve 26 which is operatively connected with the float 28. The float chamber is provided with a first discharge opening at 72 and a second discharge opening at 74, the arrangement being such that as the liquid level in chamber 24 rises the valve 26 is opened to permit liquid to flow through opening 72 into the line 36. As the liquid level in chamber 24 drops the float 28 is depressed so as to close the valve 26 and thereby discontinue supply of liquid to line 36. The arrangement is such as to eliminate the possibility of gas from the condenser escaping to the evaporator through line 36.

Port 74 feeds liquid to a line 7-6 which is, as shown in the drawings, relatively small as compared with the size of line 36. Line 76 is continuously supplied with liquid from the chamber 24, but it does not subtract appreciable quantities of liquid, and the operation of valve 26 is not seriously affected by the presence of line 76. Line 76 feeds the pump 52 with liquid and said pump discharges a high pressure spray through the small line 76a in the manner of the previously described pump (FIG. 2).

In the FIG. 6 embodiment the discharge line 50 from the motor is relatively large as compared with the liquid line 76 in order to prevent the setting up of such a high pressure condition in line 59 as would appreciably interfere with flow of refrigerant through the motor parts.

Each of the illustrated embodiments provides for the pressure feeding of liquid refrigerant directly into the motor windings as distinguished from a coolant jacket structure. The use of direct refrigerant introduction into the 'motor windings is generally preferred over jacket arrangements, but for certain purposes of the invention the refrigerant can be directed through a jacket structure wholly or partially surrounding the motor while still obtaining satisfactory operational results.

As used herein, the term motor is to be construed as an electric machine having a rotor and stator separated by an annular gap.

The various drawings show different modifimtions which the invention may take, but it will be appreciated that other variations might also be resorted to without departing from the spirit of the invention as defined by the appended claims.

I claim:

1. In a refrigeration system including a motor-driven compressor, a condenser having a bottom wall, and an evaporator coupled in operable relation, and having a high pressure compressor-condenser side and a low pressure evaporator side, the improvement wherein the motor is provided with a sealed casing,

a 'liquidrefrigerant trap operably connected to the condenser to receive liquid refrigerant from the condenser,

means including a pump for removing liquid refrigerant from said trap and directing the liquid refrigerant into said casing and into the interior of the motor and into direct contact with the interior parts of the motor at a pressure greater than the pressure in the condenser to be at least partially vaporized and cool the motor,

said liquid refrigerant trap comprising a sump connected physically with the bottom wall of the condenser whereby said pump is always assured of a supply of gas-free liquid refrigerant irrespective of variations in discharge conditions in the operation of the condenser,

and means for returning refrigerant from the motor to the low pressure side of the system.

2. In a refrigeration system including a motor-driven compressor, a condenser and an evaporator coupled in operable relation, and having a high pressure compressorcondenser side and a low pressure evaporator side, the improvement wherein the evaporator is of the semi-flooded type,

the motor is provided with a sealed casing,

means including a pump and line having an inlet located in the lower portion of the evaporator to remove liquid refrigerant therefrom and distribute liquid refrigerant into said casing and into the interior of the motor and into direct contact with the interior parts of the motor at a pressure greater than the pressure in the low pressure side of the system to be at least partially vaporized to cool the motor,

and means for returning refrigerant from the motor back to the low pressure side of the system.

3. In a refrigeration system including a motor-driven compressor, a condenser and an evaporator coupled in operable relation and having a high pressure compressor condenser side and a low pressure evaporator side, the improvement wherein the motor is provided with a sealed casing,

a liquid refrigerant trap operably connected between the condenser and evaporator and having a high pressure side and a low pressure side,

means ,for removing liquid refrigerant from the high pressure side of said liquid refrigerant trap and directing the liquid refrigerant into said casing and into the interior of the motor and into direct contact with the interior parts of the motor at a pressure greater than the pressure in the high pressure side of the system to be at least partially vaporized and cool the motor,

and means for returning refrigerant from the motor back to the low pressure side of the system.

4. In a refrigeration system including a motor-driven compressor, a condenser and an evaporator coupled in operable relation, and having a liquid refrigerant segment and a low-pressure segment, the motor including a rotor and stator separated by an annular gap,

the improvement wherein the motor is provided with a sealed casing,

means including a conduit connected between the liquid segment and said casing, spray means connected to said conduit and positioned to discharge liquid refrigerant into said casing and directly into the interior of the motor gap and into direct contact with the interior parts of the motor to be at least partially vaporized and cool the motor, I

means for boosting the pressure of liquid refrigeran passed through said spray to a level higher than system pressures,

and means for returning refrigerant from the motor directly to the low pressure side of the system.

5. In a refrigeration system including a motor-driven compressor, a condenser and an evaporator coupled in operable relation, and having a high pressure compressor-condenser side and a low pressure evaporator side,

, the motor including a rotor and stator separated by an annular gap, the improvement wherein the motor is provided with a sealed casing,

a liquid refrigerant trap operably connected to the condenser to receive liquid refrigerant from the condenser,

means including a pump for removing liquid refrigerant from said trap and directing the liquid refrigerant into said casing and into the interior of the motor gap and into direct contact with the interior parts of the motor at a pressure greater than the pressure in the high pressure side of the system to be at least partially vaporized and cool the motor,

and means for returning refrigerant from the motor directly to the low pressure side of the system.

6. In a refrigeration system having a refrigerant circulating therethrough and including a compressor and a condenser comprising the high pressure side of the system, and an evaporator comprising the low pressure side of the system, the improvement of an electric motor for driving said compressor, said motor having a sealed casing, means for conducting liquid refrigerant only from said condenser to said motor casing, and means for injecting said liquid refrigerant into said motor casing and into direct contactwith the interior parts of the motor at a pressure greater than the pressure in said condenser to assure an adequate supply of liquid refrigerant to the motor to be at least partially vaporized for cooling under severe operating conditions, and exhaust means for the spent refrigerant leading from said motor casing to the low pressure side of said system.

7. In arefrigeration system having a refrigerant circulating therethrough and including a compressor, a condenser, an evaporator and a motor driving the compressor, the improvement of means for cooling the motor including a hermetically sealed casing around the motor, a line for conducting liquid refrigerant only from the high pressure side of said system to said motor, pump means in said line effective to inject the liquid refrigerant into said motor casing under pressure greater than said system pressure, exhaust port means in said motor casing, and conduit means for spent refrigerant extending from said exhaust port means to the low pressure side of said system.

8. The combination of claim 7 wherein the exhaust means extends from said motor casing to the refrigerant line leading into the evaporator.

9. In a method of operating a refrigeration system having a compressor, a high-pressure side with both gaseous and liquid refrigerant therein, and a low pressure side, and with an encased electric motor driving the compressor, the steps of withdrawing liquid refrigerant only from the high pressure side of the system,

injecting the liquid refrigerant into the interior of the motor and into direct contact with the interior parts of the motor at a pressure greater than the pressure in the high side of the system to be at least partially vaporized and cool the motor,

and exhausing the refrigerant from the motor into the low pressure side of the system.

10. For use in a refrigeration system including a powerdriven compressor, a condenser and an evaporator coupled in operable relation and having a high-pressure cornpressor-condenser side and a low pressure evaporator side,

an electric machine having a rotor and stator and provided with a sealed casing,

a flow control liquid refrigerant trap operably connected between the condenser and evaporator and having a high pressure side and a low pressure side with a control float on the low pressure side of a liquid flow valve operably connected thereto, whereby the line connecting the condenser to the float is retained liquid full,

means for removing liquid refrigerant from said connecting line and directing the refrigerant into said casing and into the interior of said machine and into direct contact with the interior parts of said machine at a pressure greater than the pressure in the high pressure side of the system to be at least partially vaporized and cool said machine, comprising a pump operably connected between said connecting line and said machine.

11. For cooling by a refrigeration system including a power-driven compressor, a condenser and an evaporator coupled in operable relation, and having a high pressure compressor-condenser side and a low pressure evaporator Side,

an electric machine having a rotor and a stator and provided with a sealed casing,

a liquid refrigerant trap comprising a sump connected physically with the bottom of the condenser to provide a supply of gas-free liquid refrigerant irrespective of variations in discharge conditions in the operation of the condenser.

conduit means connected between said sump and said casing for removing liquid refrigerant from said sump and directing the liquid refrigerant into said casing and into the interior of said machine and into direct contact with the interior parts of said machine to be at least partially vaporized and cool said machine,

means in said conduit for boosting pressureof the liquid refrigerant entering said machine above system pressures, and means for returning refrigerant from said machine to the low pressure side of the system. 12. In a method of cooling an electric machine having a stator and rotor and a sealed easing enclosing the stator and rotor, and utilizing liquid refrigerant from a refrigeration system; the system including high and low pressure sections with a liquid refrigerant section partly in each of the high and low pressure sections, the steps of:

introducing liquid refrigerant from the liquid refrigerant section into sealed casing and into the interior of the machine and into direct contact with the stator and rotor of the machine under pressure greater than system pressures to be at least partially vaporized and cool the machine, and returning refrigerant from the machine back to the low pressure side of the system. 13. In a method of cooling an electric machine having a stator and rotor and a sealed casing enclosing the stator and rotor, and utilizing liquid refrigerant from a refrigeration system; the system including high and low pressure sections with a liquid refrigerant section partly in each of the high and low pressure sections, the steps of:

introducing liquid refrigerant from the liquid refrigerant section into the casing of the machine at a pressure greater than the high pressure section of the refrigeration system and into the interior of the machine and into direct contact with the stator and rotor of the machine to he at least partly vaporized and cool the machine, and returning refrigerant from the machine back to the low pressure side of the system.

References fitted in the file of this patent UNITED STATES PATENTS 1,960,576 Dennedy May 29, 1934 2,746,269 Moody May 22, 1956 2,768,511 Moody Oct. 30, 1956 2,770,106 Moody Nov. 13, 1956 2,776,542 Cooper Jan. '8, 1957 2,793,506 Moody May 28, 1957 2,891,391 Kocher et al June 23, 1959 2,963,878 Beggs Dec. 12, 1960 FOREIGN PATENTS 1,232,820 France Apr. 25, 1960 

13. IN A METHOD OF COOLING AN ELECTRIC MACHINE HAVING A STATOR AND ROTOR AND A SEALED CASING ENCLOSING THE STATOR AND ROTOR, AND UTILIZING LIQUID REFRIGERANT FROM A REFRIGERATION SYSTEM; THE SYSTEM INCLUDING HIGH AND LOW PRESSURE SECTIONS WITH A LIQUID REFRIGERANT SECTION PARTLY IN EACH OF THE HIGH AND LOW PRESSURE SECTIONS, THE STEPS OF: INTRODUCING LIQUID REFRIGERANT FROM THE LIQUID REFRIGERANT SECTION INTO THE CASING OF THE MACHINE AT A PRESSURE GREATER THAN THE HIGH PRESSURE SECTION OF THE REFRIGERATION SYSTEM AND INTO THE INTERIOR OF THE MACHINE AND INTO DIRECT CONTACT WITH THE STATOR AND ROTOR OF THE MACHINE TO BE AT LEAST PARTLY VAPORIZED AND COOL THE MACHINE, AND RETURNING REFRIGERANT FROM THE MACHINE BACK TO THE LOW PRESSURE SIDE OF THE SYSTEM. 